LITERATURE REVIEW J Neurosurg Spine 27:540–551, 2017 ABBREVIATIONS LL = lumbar lordosis; MCID = minimum clinically important difference; ODI = Oswestry Disability Index; PDSI = primary degenerative sagittal imbalance; PI = pelvic incidence; PJK = proximal junctional kyphosis; PT = pelvic tilt; SVA = sagittal vertical axis; TK = thoracic kyphosis; VAS = visual analog scale. SUBMITTED October 2, 2016. ACCEPTED March 3, 2017. INCLUDE WHEN CITING Published online August 11, 2017; DOI: 10.3171/2017.3.SPINE161134. Effectiveness of deformity-correction surgery for primary degenerative sagittal imbalance: a meta-analysis Chang-Hyun Lee, MD, 1 Chun Kee Chung, MD, PhD, 2–5 Jee-Soo Jang, MD, PhD, 6 Sung-Min Kim, MD, PhD, 7 Dong-Kyu Chin, MD, PhD, 8 Jung-Kil Lee, MD, PhD, 9 Seung Hwan Yoon, MD, PhD, 10 Jae Taek Hong, MD, PhD, 11 Yoon Ha, MD, PhD, 12 Chi Heon Kim, MD, PhD, 2–4 and Seung-Jae Hyun, MD, PhD, 13 on behalf of the Korean Spinal Deformity Research Society 1 Department of Neurosurgery, Ilsan Paik Hospital, Inje University College of Medicine, Goyang; 2 Department of Neurosurgery, Seoul National University Hospital, Seoul National University College of Medicine; 3 Neuroscience Research Institute, Seoul National University Medical Research Center; 4 Clinical Research Institute, Seoul National University Hospital; 5 Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul; 6 Department of Neurosurgery, Nanoori Suwon Hospital, Suwon; 7 Department of Neurosurgery, Spine Center, Kyung Hee University Hospital at Gangdong, Seoul; 8 Department of Neurosurgery, Spine and Spinal Cord Institute, Gangnam Severance Spine Hospital, Yonsei University College of Medicine, Seoul; 9 Department of Neurosurgery, Chonnam University Hospital, Chonnam University College of Medicine, Gwangju; 10 Department of Neurosurgery, Inha University Hospital, Inha University College of Medicine, Incheon; 11 Department of Neurosurgery, St. Vincent’s Hospital, College of Medicine, The Catholic University of Korea, Suwon; 12 Department of Neurosurgery, Yonsei University College of Medicine, Severance Hospital, Seoul; and 13 Department of Neurosurgery, Spine Center, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seoul, Republic of Korea OBJECTIVE As life expectancy continues to increase, primary degenerative sagittal imbalance (PDSI) is diagnosed in an increasing number of elderly people. Although corrective surgery for this sagittal deformity is becoming more popular, the effectiveness of the procedure remains unclear. The authors aimed to collate the available evidence on the effective- ness and complications of deformity-correction surgery in patients with PDSI. METHODS The authors carried out a meta-analysis of clinical studies regarding deformity correction in patients with PDSI. The studies were identifed through searches of the PubMed, Embase, Web of Science, and Cochrane databases. Surgery outcomes were evaluated and overall treatment effectiveness was assessed in terms of the minimum clinically important difference (MCID) in Oswestry Disability Index (ODI) values and pain levels according to visual analog scale (VAS) scores and in terms of restoration of spinopelvic parameters to within a normal range. Data are expressed as mean differences with 95% CIs. RESULTS Ten studies comprising 327 patients were included. The VAS and ODI values improved after deformity-cor- rection surgery. The smallest treatment effect exceeded the MCID for VAS values (4.15 [95% CI 3.48–4.82]) but not for ODI values (18.11 [95% CI 10.99–25.23]). At the fnal follow-up visit, the mean lumbar lordosis angle ( -38.60° [95% CI -44.19° to -33.01°]), thoracic kyphosis angle (31.10° [95% CI 24.67°–37.53°]), C-7 sagittal vertical axis (65.00 mm [95% CI 35.27–94.72 mm]), and pelvic tilt angle (30.82° [95% CI 24.41°–37.23°]) remained outside their normal ranges. Meta- regression analyses revealed a signifcant effect of ODI change in relation to lumbar lordosis change (p = 0.004). After a mean of 2 years after deformity correction, the mean lumbar lordosis angle and C-7 sagittal vertical axis decreased by 5.82° and 38.91 mm, respectively, and the mean thoracic kyphosis angle increased by 4.7°. The incidences of proximal junctional kyphosis and pseudarthrosis were 23.7% and 12.8%, respectively. CONCLUSIONS Deformity correction substantially relieves back pain for about 2 years in adult patients with PDSI. Suf fcient surgical restoration of lumbar lordosis can lead to substantial improvement in patient disability and reduced decompensation. Deformity correction represents a viable therapeutic option for patients with PDSI, but further technical advancements are necessary to achieve suf fcient lumbar lordosis and reduce complication rates. https://thejns.org/doi/abs/10.3171/2017.3.SPINE161134 KEY WORDS degenerative; sagittal; imbalance; deformity; meta-analysis; lumbar ©AANS, 2017 J Neurosurg Spine Volume 27 • November 2017 540 Unauthenticated | Downloaded 03/14/22 11:53 PM UTC